Are there Guidelines on Tyre and Wheel Rims?
The Australian Design Rules (ADRs) regulate what changes can be made to the tyres or wheels on a vehicle, and these vary between passenger vehicles, trucks and construction vehicles.
ADRs 23, 24 and 42 specify the requirements of strength, construction and standard pressure/load ratings for passenger car tyres and requires all vehicles to be fitted with a tyre placard that clearly documents the correct tyre specifications (size, capacity rating, speed rating, and suggested inflation pressure), Whilst it does not specify what construction style the tyres must be, it does require certain performance standards be met with respect to heat resistance, endurance, strength, and high speed stability.
It also requires some basics - that every tyre have the size, construction type, speed rating, load rating and date of manufacture clearly printed on the sidewall, as well as an arrow showing the direction of fitment (for asymmetrical tyres) and a minimum of four equally spaced tyre tread wear indicators. These are designed to show when there is 1.6mm or less tread remaining (this is the point at which a tyre is deemed to no longer be roadworthy).
Aftermarket or replacement wheels and tyres fitted to passenger vehicles must not be more than 15mm larger or smaller than the largest and smallest tyre sizes respectively listed on the manufacturer's tyre placard. Other key specifications - such as the speed and load rating - shown on the placard must also be met when installing non-original equipment tyres. They must also have the same stud pattern and spacing as the factory fitted wheels and the regulation does not permit new spacers that widen the wheels to be fitted. If the new wheels create a situation that requires the brake calipers or rotors to be modified in any way, then these wheels cannot be used without having a Vehicle Assessment Signatory Scheme (VASS) certificate provided by an certified engineer.
Other regulations may vary by State, so be sure to check those requirements carefully. The following is a very basic outline of those requirements, but please check with your local authorities as to what is permissible in your state:
Victoria:
The maximum width of any replacement wheel cannot be more than 25mm or one inch greater than the widest wheel specified by the manufacturer for that vehicle or model. The overall diameter of the wheel cannot be more than 15mm more than manufacturer's specification, and the wheel and tyre combination are not allowed to contact any part of the body or suspension when in use, nor protrude past the edge of the bodywork.
New South Wales:
The maximum width of any replacement wheel cannot be more than 26mm wider than the widest wheel specified by the manufacturer for that vehicle or model. Over this size requires an inspection by the Roads and Traffic Authority (RTA). The wheel track (the distance measured across an axle from the centre line of one tyre tread to the centre line of the opposite tyre tread) must not be greater than 25mm beyond manufacturer’s specification. Additionally, the diameter of the new wheel and tyre combination can’t be more than 15mm beyond the largest diameter combination specified by the manufacturer for that vehicle. Finally, the wheel and tyre combination are not allowed to contact any part of the body or suspension when in use, nor protrude past the edge of the bodywork.
Queensland:
The maximum width of any replacement wheel cannot be more than 15mm wider (or 26mm thinner) than the widest wheel specified by the manufacturer for that vehicle or model. The maximum tyre width allowed is 1.3 times the width of the largest optional tyre offered by the manufacturer. Wheel spacers are not permitted at all (except for those fitted by the manufacturer) and no adjustments that facilitate the fitment of larger wheels or tyres can be made to the steering limit stops. Finally, the wheel and tyre combination are not allowed to contact any part of the body or suspension when in use, nor protrude past the edge of the bodywork.
Northern Territory:
The maximum width of any replacement wheel cannot be more than 25mm wider than the widest wheel specified by the manufacturer for that vehicle or model and the wheel track must exceed 50mm beyond manufacturer’s specification. Wheel spacers are not permitted at all (except for those fitted by the manufacturer). Finally, the wheel and tyre combination are not allowed to contact any part of the body or suspension when in use, nor protrude past the edge of the bodywork.
Western Australia:
The maximum width of any replacement wheel cannot be more than 25mm or one inch greater than the widest wheel specified by the manufacturer for that vehicle or model. The overall wheel width cannot exceed 177.8mm (seven inches) unless specified by the manufacturer, and vehicles already equipped with 177.8mm wheels cannot go any larger whatsoever. The wheel track must not be greater than one inch or 25mm beyond manufacturer’s specification.
Rim diameters can’t exceed those specified by the manufacturer, although “plus one” and “plus two” wheels and tyres are allowed so long as the overall diameter of the large rims and fitted low profile tyres don’t exceed the manufacturer’s diameter specification. Finally, the wheel and tyre combination are not allowed to contact any part of the body or suspension when in use, nor protrude past the edge of the bodywork.
South Australia:
The maximum width of any replacement wheel cannot be more than 15mm wider (or thinner) than the widest wheel specified by the manufacturer for that vehicle or model. The overall diameter of the wheel cannot be more than 50mm more than manufacturer's specification, and the wheel and tyre combination are not allowed to contact any part of the body or suspension when in use, nor protrude past the edge of the bodywork. Wheel spacers are not permitted at all (except for those fitted by the manufacturer). Vehicles manufactured on or after the 01-Ju-1988 must have a speedometer that is accurate to within +/- 10% of the actual speed for all speeds above 40km/h.
Tasmania:
The maximum width of any replacement wheel cannot be more than 26mm wider than the widest wheel specified by the manufacturer for that vehicle or model and the wheel track must exceed 50mm beyond manufacturer’s specification. Wheel spacers are not permitted at all (except for those fitted by the manufacturer). Finally, the wheel and tyre combination are not allowed to contact any part of the body or suspension when in use, nor protrude past the edge of the bodywork.
Other Considerations:
For All Wheel Drive or 4x4 vehicles: To protect your AWD/4x4 system, it is important that the difference in tyre size across axles is minimised. Always ensure all four tyres on your vehicle are the same size, type, brand, and model, and rotate tyres at the recommended intervals. When replacing any tyres, if the remaining tyres on the vehicle are significantly worn, replace all four tyres. If any matching tyres (of the same size, type, brand, and model) are unavailable, replace all four tyres.
For advice on Tyre Specifications for your vehicle, please check your owners manual. You can download an online version here. You can also seek guidance from your local Ford Dealership.